The moment I knew Nolan and Heath had nailed the Joker was the opening dialogue in the second trailer:

"You've changed things...forever. There's no going back. You see to them, you're just a freak....like me!"

Classic Joker dialogue, the shots of a defeated Bruce still sitting in his batsuit, Batman crashing onto a van, and the sweeping shot of Batman on the tall building, all culminating to the iconic shot of the Joker standing in the middle of the street looking deranged as hell. Those were just glimpses of the epic moral battle between the two that would ensue in TDK.